In reality, a 5 MHz probe only needs a sampling frequency of 25 MHz. But, instead of lowering the sampling frequency (100 MHz), sub-sampling is used.
- The sub-sampling rate is chosen at 1 in 4 for a 5 MHz probe. It means that only 1 sample out of 4 will be displayed and recorded
- Groups of 4 samples are created. The sample with the highest amplitude in the group is kept and placed at the position of the first sample of the group
- The signal is recreated from the points
- All digital signals are treated simultaneously
Sub-sampling is a good way to reduce the size of recorded files without the risk of loosing important amplitude peaks.